Objective: To investigate the absorption kinetics of spinosin in the gastrointestinal of rat

to provide the biological pharmaceutical basis for dosage design. Method: The absorption kinetics was investigated in rats using situ perfusion method. RP-HPLC was used to determine the concentrations of spinosin. Result: The absorption percentages at concentration of (10

20

40 mg·L-1) in stomach were 20.35%

21.88%

20.23%

respectively. The absorption rate constant (Ka) in duodenum

jejunum

ileum and colon were (0.0264±0.0014)

(0.0234±0.0009)

(0.0226±0.0009)

(0.0265±0.0006) h-1

respectively. Intestinal Ka of spinosin at different concentrations(10

20

40 mg·L-1)were (0.0231±0.0015)

(0.0241±0.0016)

(0.0233±0.0029)h-1

respectively. Ka at pH of 6.5

7.2 and 7.8 for the whole intestine were (0.0235±0.0015)

(0.0241±0.0016)

(0.0221±0.0026)h-1. Conclusion: Spinosin was absorbed in all segments in the pattern of first-order kinetics with the passive diffusion absorption mechanism;concentration and pH of the drug solution have no effect on the absorption kinetics;the absorption at duodenum

colon

jejunum and ileum align in a decreasing order. Spinosin was well absorbed at stomach.